QDockWidget default title not respecting setContentsMargins

#include <QtWidgets\QApplication>
#include <QtWidgets\QMainWindow>
#include <QtWidgets\QDockWidget>

int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	app.setApplicationName("Dock Margins Example");
	QMainWindow mainWin;
	// setup widgets
	QDockWidget exampleDock(&mainWin);
	QWidget dockContents;
	dockContents.setStyleSheet(QStringLiteral("background: #FFFFFF;")); // contents colouring
	exampleDock.setWidget(&dockContents);
	mainWin.addDockWidget(Qt::LeftDockWidgetArea, &exampleDock);
	exampleDock.setWindowTitle("Example Dock");
	exampleDock.setContentsMargins(30, 30, 30, 30);
	mainWin.show();
	return app.exec();
}